This invention relates to recovering viscous petroleum from petroleum-containing formations. Throughout the world there are many deposits of high-viscosity crude petroleum in subsurface formations; some of these deposits are referred to as oil sands. In general, the crude petroleum in these deposits is not recoverable in its natural state through a well by ordinary production methods because there is insufficient or non-existent natural drive mechanisms to cause the petroleum to flow into a well.
There have been many in-situ well-to-well pilots proposed for shallow deposits of oil sands, all of which used some form of thermal stimulation after establishing communication between an injector well and a producer well. Many processes have been utilized in attempting to recover viscous petroleum from viscous oil formations of the Athabasca Tar Sands type, including the application of heat to such viscous petroleum formations by steam or underground combustion. The use of vertical slotted liners positioned in the viscous oil formation as a conduit for hot injection fluids has also been suggested; however, most of these methods have not been overly successful because of the difficulty of establishing and maintaining communication between an injector well and a producer well. Clearly, if one could eliminate the need to establish and maintain communication between an injector well and a producer well, regardless of the drive fluid or recovery technique employed, many of these viscous petroleum deposits could become potentially successful projects. Further, techniques are needed to assist in lifting the produced viscous petroleum to the wellhead and for clearing from the well formation solids produced with the viscous petroleum.